1. Field of the Invention
The present invention relates to a planographic printing plate feeding apparatus, and more particularly, to a planographic printing plate feeding apparatus capable of feeding planographic printing plates one sheet at a time from a laminated stack in which laminated sets comprise planographic printing plates and slip-sheets.
2. Description of the Related Art
Generally, it is often the case that in a planographic printing plate, a protective slip-sheet is attached to the image recording surface thereof to constitute a laminated set, and the plural sets are laminated on one another in a thickness direction to constitute a stack of planographic printing plates. When images are to be recorded on planographic printing plates using an exposure apparatus, it is necessary to extract planographic printing plates from a stack of plates one sheet at a time and feed them to the exposure apparatus.
For example, in an image-recording material sheet-feeder described in Japanese Patent Application Laid-Open No. 2003-182904, printing plates and slip-sheets are alternately laminated and accommodated in a cassette of a sheet conveyance unit, a suction cup suctions the slip-sheet and the printing plate from above and the suction cup moves upward to extract them from the cassette. After the slip-sheet and the printing plate are extracted, the slip-sheet is suctioned by a fan and separated from the printing plate. With this structure, however, use of a suction cup for feeding a printing plate is potentially disadvantageous in terms of the structure being complicated and the cost of the apparatus increasing.
Japanese Patent Application Laid-Open No. 60-202028 describes a structure in which a slip-sheet located at an end surface in the laminated direction of the stack is fed by a roller, and a planographic printing plate is fed by a vacuum pad. According to this structure, however, since the planographic printing plates or the slip-sheets are extracted one sheet at a time, when the slip-sheet is located at the end surface in the laminated direction, the next planographic printing plate can be extracted only after this slip-sheet is extracted and, therefore, it takes time to feed the printing plates. Further, independent feeding mechanisms are required for both the planographic printing plate and the slip-sheet, which is potentially disadvantageous in terms of the number of parts being increased, and the apparatus being increased in size and cost.